1. Field of the Invention
The present invention generally relates to lining the interior of a host conduit (e.g., pipe, vessel, etc.) with a liner material to repair or reinforce the conduit or separate the conduit from materials that are contained or transported through the newly formed liner within the conduit. More particularly, an embodiment of the invention relates to fixing a liner material into a conduit with curable material wherein spacers are inserted between at least a portion of the liner material and the conduit in order to calibrate the thickness of the liner material and to create communication channels lengthwise along the conduit for housing devices such as wires and fiber optic cables for carrying communication signals. The host conduit can be any pipe for containing fluids, gases, solids, or mixtures thereof, including a sewer pipe, oil pipeline, gas line, pipe for containing industrial chemicals, water pipe, a pipe for containing saltwater in an oilfield, etc.
2. Description of the Related Art
Various methods exist for restoring or replacing underground pipes such as sewer pipes that have corroded or crumbled. Access to such pipes is often difficult and the excavation required to dismantle and/or remove the pipes can be expensive, disruptive, and time-consuming.
U.S. Pat. No. 4,064,211, issued on Dec. 20, 1977 to Wood, relates to a “method of lining passageways in which a flexible tubular member is progressively fed into the passageway and is pressed by fluid pressure against the surface to be lined.” (Col. 1, lines 23–27). This patent is incorporated by reference as if fully set forth herein. “The flexible tubular member is of a material that is impregnated with a synthetic resin in the liquid state.” (Col. 1, lines 27–29). Fluid pressure is used to “invert” the tubular member through the passageway. (Col. 1, lines 42–58). “Upon hardening, the resin causes the tubular member to form a rigid lining in the passageway.” (Col. 1, lines 29–31).
U.S. Pat. No. 5,546,992, issued on Aug. 20, 1996 to Chick et al., relates to a dual containment pipe rehabilitation system that contains a “crush-resistant spacer disposed about the impervious primary containment pipe to form a uniform annular space.” (Col. 2, lines 16–17). This patent is incorporated by reference as if fully set forth herein. A “resin absorbing material” is impregnated with a resin prior to eversion of the liner into the pipe. (Col. 5, lines 16–21). Resin is not injected into the uniform annular space. Instead, an “impervious material 19 is provided . . . to prevent resin . . . from migrating into annular space 17.” (Col. 5, lines 21–24).
An important aspect of “presoaking” methods such as that disclosed by Wood and Chick et al., in the above-mentioned patents is that a fiber or fabric-type tube is impregnated with resin before it is installed into the host conduit. One disadvantage of such systems is the increased costs associated with having to presoak the fabric with resin before it is inserted within the host conduit. Special equipment is required to “wet” the fabric, and it is difficult to handle the “wet” fabric while attempting to install it into the host conduit. Another disadvantage of these systems is the relatively high cost of the fabric or fiber and the relatively high labor costs associated with fabricating the tubes. Additionally, the use of “presoaking” methods typically results in “fiber-weakening,” which causes a reduction in strength of the newly formed liner and its capacity to hold pressurized fluids.
Other methods exist to place a liner in a pipe or vessel without presoaked fabric tubes. One disadvantage that typically occurs in methods lacking presoaked fabric tubes is the inability to adequately control “slump” of resin toward the bottom of the pipe or vessel. “Slump” is the tendency of matter to respond to the force of gravity and to settle to the bottom of the pipe or vessel, which makes it difficult or impossible to control the evenness of the newly cured lining within the host conduit. Such slump distorts the thickness of the new liner by causing uneven thickness of the wall of the newly formed lining and usually causes the lining to have a thicker bottom and a thinner top. In order to reduce slump, it has been necessary in some methods to use a relatively viscous resin that will resist flowing under the force of gravity in order to allow the resin to be cured before it has settled near the bottom of the host conduit.
U.S. Pat. No. 5,762,450, issued on Jun. 9, 1998 to Schmager, relates to a system and method for relining a sewer pipe section that uses inliners and a plurality of nubs that serve as spacers to reserve an annular space between the inliners. (Col. 3, lines 12–17). This patent is incorporated by reference as if fully set forth herein. Separations between the nubs, however, make the nubs ineffective for preventing slump of resin toward the bottom of the sewer pipe.
Therefore, there remains a need in the art for an apparatus and method for more easily and efficiently installing a liner into a host conduit with minimal trenching and excavation and without the disadvantages of fiber-weakening and slump.